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From: John Garry <john.garry@huawei.com>
To: Michael Kelley <mikelley@microsoft.com>,
	Dexuan Cui <decui@microsoft.com>,
	KY Srinivasan <kys@microsoft.com>,
	Stephen Hemminger <sthemmin@microsoft.com>,
	"wei.liu@kernel.org" <wei.liu@kernel.org>,
	"jejb@linux.ibm.com" <jejb@linux.ibm.com>,
	"martin.petersen@oracle.com" <martin.petersen@oracle.com>,
	Haiyang Zhang <haiyangz@microsoft.com>,
	"ming.lei@redhat.com" <ming.lei@redhat.com>,
	"bvanassche@acm.org" <bvanassche@acm.org>,
	"linux-scsi@vger.kernel.org" <linux-scsi@vger.kernel.org>,
	"linux-hyperv@vger.kernel.org" <linux-hyperv@vger.kernel.org>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"stable@vger.kernel.org" <stable@vger.kernel.org>
Subject: Re: [PATCH] scsi: storvsc: Cap scsi_driver.can_queue to fix a hang issue during boot
Date: Wed, 6 Oct 2021 17:24:00 +0100	[thread overview]
Message-ID: <fc4b3284-0218-8a03-a55c-94c10ac0b029@huawei.com> (raw)
In-Reply-To: <MWHPR21MB15932B5C5B5C5EE5CBAFE00ED7B09@MWHPR21MB1593.namprd21.prod.outlook.com>

On 06/10/2021 17:08, Michael Kelley wrote:
>>> The calculated value of can_queue is not realistic.  The blk-mq layer
>>> caps the number of tags at 10240,
>> nit: 1024, I think
> I was thinking about BLK_MQ_MAX_DEPTH (#define'd as 10240), which
> is used to limit the tag set size in blk_mq_alloc_tag_set().   When running
> on large VMs on Hyper-V, we can see the "blk-mq: reduced tag depth
> to 10240" message.:-(

Ah, right. The other related capping is the sdev queue depth, which is 
now capped at max(1024, can_queue), see scsi_device_max_queue_depth().

Thanks,
John

  reply	other threads:[~2021-10-06 16:21 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-10-06  7:03 [PATCH] scsi: storvsc: Cap scsi_driver.can_queue to fix a hang issue during boot Dexuan Cui
2021-10-06  7:17 ` Greg KH
2021-10-06  8:17 ` John Garry
2021-10-06 15:01   ` Michael Kelley
2021-10-06 16:03     ` John Garry
2021-10-06 16:08       ` Michael Kelley
2021-10-06 16:24         ` John Garry [this message]
2021-10-06 17:28       ` Dexuan Cui

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